I cant see the shared file at network sometimes, how?

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\comp1>NBTSTAT -n

Local Area Connection:
Node IpAddress: [192.168.1.70] Scope Id: []

NetBIOS Local Name Table

Name Type Status
---------------------------------------------
YANGCHIN <00> UNIQUE Registered
EDITORIAL <00> GROUP Registered
YANGCHIN <20> UNIQUE Registered
EDITORIAL <1E> GROUP Registered

C:\Documents and Settings\comp1>IPCONFIG /ALL

Windows IP Configuration

Host Name . . . . . . . . . . . . : yangchin
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller
Physical Address. . . . . . . . . : 20-CF-30-BA-52-4C
Dhcp Enabled. . . . . . . . . . . : No
IP Address. . . . . . . . . . . . : 192.168.1.70
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 202.188.1.5
202.188.0.133

C:\Documents and Settings\comp1>